A little while ago somebody on comp.compilers asked if the source for Pascal-S,
a subset Pascal compiler, assembler and interpreter described in a paper by
Wirth some years ago, was available on the net. I offered a version that I
subsequently found had been vapourized in a VAX crash some years ago. However,
by sniffing around the net I found another copy that I have modified
to run under Turbo Pascal version 5. You can get this from my ftp
server:

cscx.cs.rhbnc.ac.uk::/pub/compilers/pascals.pas

Pascal-S is written in Pascal, and forms an excellent introduction to
the art of designing small compilers. The best source for the paper is
in an edited collection by Baron entitled `Pascal - the language and
its implementation' I should think it is out of print now, but most
university libraries should have a copy. A modified version was used
by Ben-Ari in the first edition of his book on concurrency.

Adrian

PS If you are interested in this kind of thing, you might like to join the
mailing list for my RDP compiler-compiler which is a good way to start
learning about recursive descent parsers. Send me a note if you want to find
out more.